The big picture: NASA's Hubble Space Telescope recently captured something unlike anything scientists have seen before. Initially thought to be an imaging flaw, they now believe a gigantic black hole flying out of a galaxy is igniting a trail of young stars behind it.

When Pieter van Dokkum of Yale University first noticed a streak through an image from NASA's Hubble Space Telescope, he assumed a cosmic ray had created an artifact when it hit the telescope. However, further investigation revealed a unique cosmic event.

Scientists currently theorize that the streak is a 200,000 light-year-long trail of young stars left by a supermassive black hole hurling out of a galaxy. As it passes through the cloud of dust and gas surrounding the galaxy at speeds high enough to travel from Earth to the Moon in 14 minutes, the gas is shocked and heated and may form new stars as it cools behind the black hole. Researchers still aren't sure how it works. The black hole likely weighs around 20 million Suns.

Artist's impression

The circumstances leading to the phenomenon might have started with the merger of two galaxies around 50 million years ago. The supermassive black holes at the center of these galaxies possibly formed a stable binary as they orbited each other for a while. Later, a third galaxy and supermassive black hole merged with the other two, disrupting the stable orbit.

Around 39 million years ago, either the binary kicked out the third black hole, or the intruder replaced one of the original two. In any case, the event knocked the binary and the third black hole in opposite directions, possibly leaving the original galaxy without any black holes at its core.

Hubble Space Telescope image

Upon first noticing the streak, van Dokkum tried to clean it up by eliminating cosmic rays from his analysis. When the streak remained, he realized the telescope had captured something new. He and his team got further confirmation through follow-up spectroscopy at the W. M. Keck observatories in Hawaii. The researchers are also planning further investigation with the James Webb Space Telescope and the Chandra X-ray Observatory.

The research paper describing the findings is freely available in the Astrophysical Journal Letters. If more streaks like these exist in the universe, NASA's upcoming Nancy Grace Roman Space Telescope might be able to find them with the help of machine learning.